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STAT(2)                    Linux Programmer's Manual                   STAT(2)



NAME
       stat, fstat, lstat - get file status

SYNOPSIS
       #include <sys/types.h>
       #include <sys/stat.h>
       #include <unistd.h>

       int stat(const char *path, struct stat *buf);
       int fstat(int fd, struct stat *buf);
       int lstat(const char *path, struct stat *buf);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       lstat(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       These  functions return information about a file.  No permissions are required on the file itself, but -- in the
       case of stat() and lstat() -- execute (search) permission is required on all of the  directories  in  path  that
       lead to the file.

       stat() stats the file pointed to by path and fills in buf.

       lstat()  is  identical  to stat(), except that if path is a symbolic link, then the link itself is stat-ed, not
       the file that it refers to.

       fstat() is identical to stat(), except that the file to be stat-ed is specified by the file descriptor fd.

       All of these system calls return a stat structure, which contains the following fields:

           struct stat {
               dev_t     st_dev;     /* ID of device containing file */
               ino_t     st_ino;     /* inode number */
               mode_t    st_mode;    /* protection */
               nlink_t   st_nlink;   /* number of hard links */
               uid_t     st_uid;     /* user ID of owner */
               gid_t     st_gid;     /* group ID of owner */
               dev_t     st_rdev;    /* device ID (if special file) */
               off_t     st_size;    /* total size, in bytes */
               blksize_t st_blksize; /* blocksize for file system I/O */
               blkcnt_t  st_blocks;  /* number of 512B blocks allocated */
               time_t    st_atime;   /* time of last access */
               time_t    st_mtime;   /* time of last modification */
               time_t    st_ctime;   /* time of last status change */
           };

       The st_dev field describes the device on which this file resides.  (The major(3) and  minor(3)  macros  may  be
       useful to decompose the device ID in this field.)

       The st_rdev field describes the device that this file (inode) represents.

       The  st_size  field gives the size of the file (if it is a regular file or a symbolic link) in bytes.  The size
       of a symlink is the length of the pathname it contains, without a trailing null byte.

       The st_blocks field indicates the number of blocks allocated to the file, 512-byte units.  (This may be smaller
       than st_size/512 when the file has holes.)

       The  st_blksize  field  gives  the  "preferred" blocksize for efficient file system I/O.  (Writing to a file in
       smaller chunks may cause an inefficient read-modify-rewrite.)

       Not all of the Linux file systems implement all of the time fields.  Some file system types allow  mounting  in
       such  a  way  that  file and/or directory accesses do not cause an update of the st_atime field.  (See noatime,
       nodiratime, and relatime in mount(8), and related information in  mount(2).)   In  addition,  st_atime  is  not
       updated if a file is opened with the O_NOATIME; see open(2).

       The  field  st_atime  is  changed  by file accesses, for example, by execve(2), mknod(2), pipe(2), utime(2) and
       read(2) (of more than zero bytes).  Other routines, like mmap(2), may or may not update st_atime.

       The field st_mtime is changed by file modifications,  for  example,  by  mknod(2),  truncate(2),  utime(2)  and
       write(2)  (of  more than zero bytes).  Moreover, st_mtime of a directory is changed by the creation or deletion
       of files in that directory.  The st_mtime field is not changed for changes in owner, group, hard link count, or
       mode.

       The field st_ctime is changed by writing or by setting inode information (i.e., owner, group, link count, mode,
       etc.).

       The following POSIX macros are defined to check the file type using the st_mode field:

           S_ISREG(m)  is it a regular file?

           S_ISDIR(m)  directory?

           S_ISCHR(m)  character device?

           S_ISBLK(m)  block device?

           S_ISFIFO(m) FIFO (named pipe)?

           S_ISLNK(m)  symbolic link? (Not in POSIX.1-1996.)

           S_ISSOCK(m) socket? (Not in POSIX.1-1996.)

       The following flags are defined for the st_mode field:

           S_IFMT     0170000   bit mask for the file type bit fields
           S_IFSOCK   0140000   socket
           S_IFLNK    0120000   symbolic link
           S_IFREG    0100000   regular file
           S_IFBLK    0060000   block device
           S_IFDIR    0040000   directory
           S_IFCHR    0020000   character device
           S_IFIFO    0010000   FIFO
           S_ISUID    0004000   set UID bit
           S_ISGID    0002000   set-group-ID bit (see below)
           S_ISVTX    0001000   sticky bit (see below)
           S_IRWXU    00700     mask for file owner permissions
           S_IRUSR    00400     owner has read permission
           S_IWUSR    00200     owner has write permission
           S_IXUSR    00100     owner has execute permission
           S_IRWXG    00070     mask for group permissions
           S_IRGRP    00040     group has read permission
           S_IWGRP    00020     group has write permission
           S_IXGRP    00010     group has execute permission
           S_IRWXO    00007     mask for permissions for others (not in group)
           S_IROTH    00004     others have read permission
           S_IWOTH    00002     others have write permission
           S_IXOTH    00001     others have execute permission

       The set-group-ID bit (S_ISGID) has several special uses.  For a directory it indicates that BSD semantics is to
       be  used for that directory: files created there inherit their group ID from the directory, not from the effec-
       tive group ID of the creating process, and directories created there will also get the S_ISGID bit set.  For  a
       file  that  does  not  have  the  group  execution  bit (S_IXGRP) set, the set-group-ID bit indicates mandatory
       file/record locking.

       The sticky bit (S_ISVTX) on a directory means that a file in that directory can be renamed or deleted  only  by
       the owner of the file, by the owner of the directory, and by a privileged process.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       EACCES Search permission is denied for one of the directories in the path prefix of path.  (See also path_reso-
              lution(7).)

       EBADF  fd is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
              File name too long.

       ENOENT A component of path does not exist, or path is an empty string.

       ENOMEM Out of memory (i.e., kernel memory).

       ENOTDIR
              A component of the path prefix of path is not a directory.

       EOVERFLOW
              (stat()) path refers to a file whose size cannot be represented in the type       off_t.  This can occur
              when  an application compiled on a 32-bit platform without -D_FILE_OFFSET_BITS=64 calls stat() on a file
              whose size exceeds (2<<31)-1 bits.

CONFORMING TO
       These system calls conform to SVr4, 4.3BSD, POSIX.1-2001.

       Use of the st_blocks and st_blksize fields may be less portable.  (They were introduced in BSD.  The  interpre-
       tation differs between systems, and possibly on a single system when NFS mounts are involved.)

       POSIX  does  not  describe  the S_IFMT, S_IFSOCK, S_IFLNK, S_IFREG, S_IFBLK, S_IFDIR, S_IFCHR, S_IFIFO, S_ISVTX
       bits, but instead demands the use of the macros S_ISDIR(), etc.  The S_ISLNK() and S_ISSOCK() macros are not in
       POSIX.1-1996, but both are present in POSIX.1-2001; the former is from SVID 4, the latter from SUSv2.

       Unix  V7  (and  later  systems)  had  S_IREAD,  S_IWRITE, S_IEXEC, where POSIX prescribes the synonyms S_IRUSR,
       S_IWUSR, S_IXUSR.

   Other Systems
       Values that have been (or are) in use on various systems:

       hex    name       ls   octal    description
       f000   S_IFMT          170000   mask for file type
       0000                   000000   SCO out-of-service inode; BSD unknown
                                       type; SVID-v2 and XPG2 have both
                                       0 and 0100000 for ordinary file
       1000   S_IFIFO    p|   010000   FIFO (named pipe)
       2000   S_IFCHR    c    020000   character special (V7)
       3000   S_IFMPC         030000   multiplexed character special (V7)
       4000   S_IFDIR    d/   040000   directory (V7)
       5000   S_IFNAM         050000   XENIX named special file
                                       with two subtypes, distinguished by
                                       st_rdev values 1, 2
       0001   S_INSEM    s    000001   XENIX semaphore subtype of IFNAM
       0002   S_INSHD    m    000002   XENIX shared data subtype of IFNAM
       6000   S_IFBLK    b    060000   block special (V7)
       7000   S_IFMPB         070000   multiplexed block special (V7)
       8000   S_IFREG    -    100000   regular (V7)
       9000   S_IFCMP         110000   VxFS compressed
       9000   S_IFNWK    n    110000   network special (HP-UX)
       a000   S_IFLNK    l@   120000   symbolic link (BSD)
       b000   S_IFSHAD        130000   Solaris shadow inode for ACL
                                       (not seen by userspace)
       c000   S_IFSOCK   s=   140000   socket (BSD; also "S_IFSOC" on VxFS)
       d000   S_IFDOOR   D>   150000   Solaris door
       e000   S_IFWHT    w%   160000   BSD whiteout (not used for inode)
       0200   S_ISVTX         001000   sticky bit: save swapped text even

                                       after use (V7)
                                       reserved (SVID-v2)
                                       On non-directories: don't cache this
                                       file (SunOS)
                                       On directories: restricted deletion
                                       flag (SVID-v4.2)
       0400   S_ISGID         002000   set-group-ID on execution (V7)
                                       for directories: use BSD semantics for
                                       propagation of GID
       0400   S_ENFMT         002000   System V file locking enforcement (shared
                                       with S_ISGID)
       0800   S_ISUID         004000   set-user-ID on execution (V7)
       0800   S_CDF           004000   directory is a context dependent
                                       file (HP-UX)

       A sticky command appeared in Version 32V AT&T UNIX.

NOTES
       Since kernel 2.5.48, the stat structure supports nanosecond resolution for the  three  file  timestamp  fields.
       Glibc  exposes  the  nanosecond  component of each field using names either of the form st_atim.tv_nsec, if the
       _BSD_SOURCE or _SVID_SOURCE feature test macro is defined, or of the form st_atimensec,  if  neither  of  these
       macros  is  defined.   On  file  systems that do not support sub-second timestamps, these nanosecond fields are
       returned with the value 0.

       On Linux, lstat() will generally not trigger automounter action, whereas stat() will.

       For most files under the /proc directory, stat() does not return the file size in the  st_size  field;  instead
       the field is returned with the value 0.

   Underlying kernel interface
       Over  time,  increases  in  the  size  of  the  stat structure have led to three successive versions of stat():
       sys_stat() (slot __NR_oldstat), sys_newstat() (slot __NR_stat), and  sys_stat64()  (new  in  kernel  2.4;  slot
       __NR_stat64).   The  glibc  stat()  wrapper  function  hides these details from applications, invoking the most
       recent version of the system call provided by the kernel, and repacking the returned  information  if  required
       for old binaries.  Similar remarks apply for fstat() and lstat().

EXAMPLE
       The following program calls stat() and displays selected fields in the returned stat structure.

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <time.h>
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           struct stat sb;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           if (stat(argv[1], &sb) == -1) {
               perror("stat");
               exit(EXIT_SUCCESS);
           }

           printf("File type:                ");

           switch (sb.st_mode & S_IFMT) {
           case S_IFBLK:  printf("block device\n");            break;
           case S_IFCHR:  printf("character device\n");        break;
           case S_IFDIR:  printf("directory\n");               break;
           case S_IFIFO:  printf("FIFO/pipe\n");               break;
           case S_IFLNK:  printf("symlink\n");                 break;
           case S_IFREG:  printf("regular file\n");            break;
           case S_IFSOCK: printf("socket\n");                  break;
           default:       printf("unknown?\n");                break;
           }

           printf("I-node number:            %ld\n", (long) sb.st_ino);

           printf("Mode:                     %lo (octal)\n",
                   (unsigned long) sb.st_mode);

           printf("Link count:               %ld\n", (long) sb.st_nlink);
           printf("Ownership:                UID=%ld   GID=%ld\n",
                   (long) sb.st_uid, (long) sb.st_gid);

           printf("Preferred I/O block size: %ld bytes\n",
                   (long) sb.st_blksize);
           printf("File size:                %lld bytes\n",
                   (long long) sb.st_size);
           printf("Blocks allocated:         %lld\n",
                   (long long) sb.st_blocks);

           printf("Last status change:       %s", ctime(&sb.st_ctime));
           printf("Last file access:         %s", ctime(&sb.st_atime));
           printf("Last file modification:   %s", ctime(&sb.st_mtime));

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       access(2), chmod(2), chown(2), fstatat(2), readlink(2), utime(2), capabilities(7), symlink(7)

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2009-04-21                           STAT(2)